Device and method for assisting inflation

ABSTRACT

The invention relates to a method for aiding inflation for a vehicle, comprising access to vehicle tire pressure ( 10 ) and temperature ( 20 ) data, an under-inflation detection module ( 50 ), and an inflation condition testing module ( 30 ) making it possible to carry out a test for detecting a possible optimal inflation condition if the following criteria are met:—there is a non-critical under-inflation state for at least one of the vehicle tires;—the tires are not in an overheated state;—and the tire state is unchanged by sunlight. When the test module ( 30 ) determines the optimal inflation condition, a signal is outputted. Such a method causes tire inflation to be carried out under favorable conditions actually corresponding to the reference value provided by the manufacturers. The invention also relates to the corresponding device for aiding inflation.

The present invention relates to a device and a method for inflationassistance for a vehicle making it possible to inform the driver that atleast one of the tyres of the vehicle must be reinflated, and toencourage him to carry out this reinflation at times when the optimalconditions are present.

Many technologies have been designed to allow motorists to carry out theinflation of the tyres after running, with no distance constraint.

Since the tyres are then at a temperature higher than the standardinflation temperature, if the standard pressure value is used directly,under-inflation is then obtained, the magnitude of which depends on thedifference between the real inflation temperature and recommendedstandard temperature.

For example, if the tyres of a vehicle are reinflated in a heated state,after running, on an indicated pressure base of 2.0 bar, when the tyreshave cooled down, it is probable that the user will obtain a significantpressure difference of the order of 130 to 180 mbar between the fronttyres and the rear tyres. Specifically, on most current motor vehicles,the temperature of the front tyres rises more than that of the reartyres. Typically, for a difference of approximately 15° C., the pressuredifference is approximately 150 mbar. If inflation is carried out whenhot with tyres having excess pressure due to the heat, and withouttaking account of this excess pressure, the result will beunder-inflation. Specifically, when the tyres cool, the excess pressuredisappears. The tyres are then under-inflated by a value depending onthe magnitude of the excess pressure induced by the heating and presentat the time of inflation.

Such a real pressure difference may have an impact on the driving of thevehicle, its road behaviour, its road holding, etc.

According to another typically-known case, the temperature differencebetween a tyre situated in the shade and a tyre situated in the sun mayreach 15° C. to 20° C. and even more. This causes an induced pressuredifference that may reach or even exceed 200 mbar, for example betweenthe tyres on the drivers side, sheltered from the sun, and the tyres onthe passenger side, exposed to the sun. If reinflation takes place insuch a context, the real pressure of the tyres when the temperatureshave returned to a balanced state could be 200 mbar less than the valueindicated during inflation when hot and therefore not only would thetyres be under-inflated relative to the recommended pressure but alsoout of balance relative to the opposite side.

Here again, such a real pressure difference may have an impact on thedriving of the vehicle, its road behaviour, its road holding, etc.

Therefore, to alleviate this situation, various means and methods areused to compensate for the inflation pressure value.

Document FR2885321 describes a solution consisting in providing meansfor analysing the pressure and temperature comparing the measured valueof the tyre's inflation pressure with a recommended pressure. The realinflation pressure is corrected according to the tyre temperatureindicated by a device for detecting tyre temperature. The referencetemperature value used is established according to the temperaturesmeasured during the latest start-ups of the said vehicle.

Document FR2667270 deals with the context specific to the inflation ofthe tyres at the factory, in order to compensate for the temperaturevariations during the inflation process. This objective is achieved byincorporating a means for automatically detecting the temperature of thecompressed air used in the inflation of the tyres and the ambienttemperature of the factory, and in adjusting the predetermined inflationpressure in order to take account of these variables. In addition, theinflation device presented incorporates a means for detecting the realinflation pressure of the wheel/tyre assembly during the inflationprocess in order to have the assurance that the temperature-compensatedinflation pressure is really obtained. This device, involving the use oftwo means for measuring the temperature (one for the ambient temperatureand the other for the temperature of the inflation air), is technicallydifficult to apply on inflation sites intended for the consumer, becausesuch sites have to be low-cost in order to be able to be present inlarge numbers over the whole road network.

Document GB2388179 describes a device in which the vehicle is fitted onthe one hand with temperature sensors making it possible to determinethe tyre temperature and on the other hand with pressure sensors.Therefore, the inflation may be carried out taking account of the realtemperature of the tyres.

Document U.S. Pat. No. 5,140,851 describes a device making it possibleto compensate for errors in measuring the temperature when the tyre airtemperature and volume are determined. A correction means based oncorrection parameters makes it possible to obtain corrected values.Furthermore, the device makes it possible to reveal a possible reductionin the tyre air volume.

Document U.S. Pat. No. 6,711,955 describes a device making it possibleto inflate the tyres in the hot state, in order to prevent having towait for the latter to cool down before carrying out the inflation. Thisdevice involves two temperature sensors in order to detect thetemperature of the tyre and of the ambient air. A processor makes itpossible to compare the temperature and pressure values with arecommended value. This device is particularly suitable for theinflation of aircraft tyres.

Document US2005162263 describes a method making it possible to inflatetyres while taking account of two distinct temperature values in orderto compensate for the effect of this temperature on the pressure. Thetemperature measurements are taken at the rim and at the brakes of thevehicle.

Document US 2006276990 describes an inflation device provided with acontroller storing a target pressure value to which the tyre should beinflated when it is at a standard temperature. Data relating to the realpressure and temperature are obtained and are used to determine a refillpressure compensated for according to the temperature.

The document FR 2.829.423 described a system for the detection of apressure decrease in a tire which contains a probe of pressure of air, atemperature sensor of the tire and a unit of evaluation. The unit ofevaluation converts the values of pressure of air and the values oftemperature measured in values of pressure of air compensated intemperature, determines the modification in the time of the values ofpressure of air compensated and generates a signal of warning if themodification in time exceeds a threshold value. The unit of evaluationdecreases the threshold value of modification of pressure of air whenthe difference between the value of pressure of air measured andcompensated in temperature compared to a value of reference of pressureof air predetermined and compensated in temperature increases.

In all these documents, it is accepted that the inflation of the tyresin the hot state has serious disadvantages that it is preferable toavoid. All these devices and methods make reference to means making itpossible to carry out an inflation at ambient temperature while making acompensation based on the one hand on pressure and temperaturemeasurements and on the other hand on compensation computations. Manysources of errors and/or inaccuracies are present both in themeasurements taken and in the computations made for the compensation.

Moreover all these documents propose systems which inform the driver ofthe vehicle when a problem of inflation exists in an unquestionable wayto limit the number of transmitted alarms. In spite of that the messagestransmitted to the driver are often not understood and call even intoquestion the confidence of these drivers towards these systems.

There is thus a real need for a process for monitoring for the tireswhich transmits to the driver simple messages, comprehensible and likelyto reinforce the confidence of the drivers for the utility of thesesystems by also facilitating the management of the inflation of thetires.

Thus, to mitigate these many disadvantages, the invention envisages amethod of assistance to the inflation of tires for vehicles equippedwith a set of tyre pressure sensors, a set of tyre temperature sensors,and computing means, wherein:

-   -   the computing means are supplied with the data relating to the        pressure of the vehicle's tyres;    -   the computing means are supplied with the data relating to the        temperature of the said tyres;    -   depending on the pressure and temperature data obtained, the        user verifies, with the aid of the computing means, a possible        under-inflation condition present on one or more tyres; and    -   if an under-inflation condition is detected, the user, with the        aid of the computing means, carries out a test in order to        reveal a possible optimal condition for inflation, if all the        following criteria are simultaneously satisfied:        -   a non-critical under-inflation condition has been detected            for at least one of the tyres of the vehicle;        -   the tyres are not in a heated state; and        -   the state of the tyres is not changed by exposure to the            sun;    -   when an optimal condition for inflation is revealed, a        corresponding signal is sent.

Such a method of assistance to the inflation of tires has the advantageto indicate to the driver when he can carry out the process of inflatingthe tyres in favourable conditions, namely conditions reallycorresponding to the reference value supplied by the manufacturers,without having to compensate according to a higher inflationtemperature. Therefore, it is possible to reduce the frequency ofinflation. An inflation carried out in good conditions also makes itpossible to optimize the performance of the tyres and of the vehicles,whether it be in terms of comfort, road holding or fuel consumption.

When the above three conditions are met: non-optimal inflation state ofthe tyres, absence of heating due to running and absence of disruptiondue to exposure to the sun, the optimum conditions for inflation areachieved. Each of these conditions is necessary and it is the fact ofverifying these three conditions simultaneously which guarantees theoptimum conditions for an effective and durable inflation.

When the above three conditions are satisfied, the state of inflation ofthe vehicle's tyres is not critical, that is to say does not require thetransmission to the driver of an imperative alert. The signal to betransmitted by the device described may therefore be an indicativesignal informing the driver that the optimum inflation conditions aresatisfied, for example a “green light”. This signal must furthermore beswitched off as soon as any one of these three conditions is no longersatisfied.

The device has the advantage of converting a usually “non-criticalalarm” message into a service designed to help the driver to inflate histyres at the most appropriate times.

The signal may make it possible to generate a motivational message(audible or visual) intended for the driver in order to warn him thatthe tyres are slightly under-inflated and that the conditions areoptimum for inflation to the recommended pressure. Usually, thiscondition is observed for a relatively short, but variable, period, oncethe vehicle is moving. It is therefore useful for the driver to be ableto identify this condition in a precise and sure way. This message orsignal may reappear every time the conditions are again satisfied.

Preferably, a non-critical under-inflation condition corresponds to ameasured inflation pressure that is less by substantially 200 to 400mbar than the nominal pressure recommended when cold. When the measuredpressure becomes less by 400 mbar and more, it is no longer possible tospeak of a non-critical condition and an alarm message to the driverbecomes imperative.

It should be noted that these values are given to illustrate the devicefor passenger vehicles. These values can very easily be adapted by askilled man for any other type of vehicles.

It is also possible to consider a “non-critical under-inflationcondition” to be the state of a vehicle's tyres in which one of thetyres is markedly less (or more) inflated than the average of the otherthree, while not having a measured inflation pressure that is less thanthe recommended inflation pressure.

According to an advantageous embodiment, the parameters of the test aredefined so that the tyres are not considered in a heated state if thedifference between the ambient temperature and the value of thetemperature of each of the tyres of the vehicle does not exceed 5° C.

According to another embodiment, the parameters of the test are definedso that the tyres are not considered in a heated state if there is lessthan 5° C. of difference between the average of the temperatures at thefront and the average of the temperatures at the rear of the vehicle.

According to a further embodiment, the parameters of the test aredefined so that the tyres are not considered in a heated state if thedifference between the tyre temperature value of the spare wheel tyreand the average of the temperatures values of the tyres of the vehicledoes not exceed 5° C.

Advantageously, the parameters of the test are defined so that the stateof the tyres is not considered changed by exposure to the sun when themaximum temperature difference between the hottest tyre and the coldesttyre does not exceed 5° C. and preferably 3° C.

These tests may be cumulative.

Advantageously, in order to reveal a possible optimal condition forinflation, the user verifies that the following criterion is alsosatisfied: the tyres are at a temperature substantially close to thatmeasured at the moment of detection of under-inflation. As an example, adifference of 0 to 5° C. will be considered negligible and bothtemperatures are then considered close.

Preferably, the inflation assistance method stops transmitting a signalencouraging inflation as soon as any one of the three conditions for anoptimum inflation condition is no longer satisfied.

The invention also provides for an inflation assistance device for avehicle comprising:

-   -   an access to a vehicle's tyre pressure data;    -   an access to the temperature data of the said tyres;    -   an under-inflation detection module making it possible,        according to the pressure and temperature data obtained, to        reveal a possible under-inflation condition present on one or        more tyres;    -   a module for testing the inflation condition, making it possible        to carry out, with the aid of computation means, a test in order        to reveal a possible optimal condition for inflation;

said device being adapted to operate the previously described method.

All the embodiment details are given in the following description,supplemented by FIGS. 1 and 2, in which:

FIG. 1 shows a functional flowchart illustrating schematically thevarious steps of the method according to the invention;

FIG. 2 shows a schematic representation of an example of an inflationassistance device according to the invention.

In the present description, the following terms are used notably for thefollowing meanings:

“Non-critical under-inflation condition” means a loss of pressure thatis substantially greater than or equal to 200 mbar relative to therecommended nominal pressure when cold. Beyond a certain threshold,advantageously set at 400 mbar, the level of under-inflation isconsidered severe. At this level, a distinct alarm for severeunder-inflation is advantageously provided. It is also possible toextend this definition to all cases in which the tyre inflationpressures are not fully satisfactory, for example when one of the tyresis markedly less (or even more) inflated than the average of the otherthree, while not having a measured inflation pressure lower than therecommended inflation pressure.

“Heating state” means a rise in temperature due to a mechanical forcesustained by the tyre, such as for example running, which generates aseries of deformations close to the portion in contact with the groundwhich sustains a partial flattening.

“Tyre pressure management and measurement system” or “tyre pressuremonitoring system”, often called “TPMS” for “Tyre Pressure ManagementSystem”, means a system making it possible at least to collect the tyrepressure values of a vehicle and to supply an “output” for example inthe form of an item of information associated with these values. Thisoutput may be an alarm due to an under-inflation situation, an item ofinformation on the pressure values present in the tyres, an alarminforming that a leak has been detected, etc. A TPMS system may operateindependently or be associated with other items of equipment of avehicle, such as for example a screen making it possible to display thevarious states and alarms.

“Pressure-related data” means data such as the absolute tyre pressurevalues and the values that are directly or indirectly associated withpressure such as the presence of a leak, the rate of pressure loss, etc.

FIG. 2 shows a schematic representation of an inflation assistancedevice 1 for a vehicle according to the invention. It comprises an inputor access to data 10 relating to the pressure from at least one tyre ofa vehicle and an input or access to data 20 relating to the temperatureof the said tyres. The data inputs are advantageously obtained by a datatransmission means such as a communication bus of the vehicle.

An under-inflation detection module 50 makes it possible to take severalmeasurements of the pressure value spaced over time. This feature makesit possible to monitor the change in the pressure value as a function oftime. By comparing this change with preset leakage threshold values, thepresence of leaks may be revealed. The detection module 50 may comprisea microprocessor or another computing means, and test commands orinstructions.

An inflation condition test module 30, having access on the one hand tothe pressure-related data 10 and on the other hand to thetemperature-related data 20 of at least one tyre of the vehicle, makesit possible to detect a possible optimum condition for inflation. Thetest module 30 may comprise a microprocessor or other computing means,and test commands or instructions. The test parameters 40, stored in thedevice, or supplied before a test is run, make it possible to configurethe test module so that the latter can identify the cases in which anoptimum condition for inflation is or is not present. FIG. 1, describedlater, makes it possible to illustrate the operating principle of thetest module.

If there is an optimum condition for inflation, an optimal condition forinflation output allows the transmission of a corresponding signal.Furthermore, if an optimal condition for inflation is detected, the testmodule continues the analysis of the signal, either to ascertain thatthe condition is maintained or, on the contrary, that the conditionceases, because one or more criteria are no longer satisfied. The methodtherefore operates in a loop.

The optimal condition for inflation signal may be used to send a messageto the user, by the intervention of a visual or audible means. The meansfor processing the output signal, the display means, and other elementsallowing such functions may be provided outside the inflation assistancedevice 1. A wire or microwave link then allows the data transfers.

The device and the method according to the invention are advantageouslyprovided either for integration into a tyre pressure management system(TPMS), or in order to interact, notably by data interchange, with sucha system. Therefore, the pressure-related and temperature-related dataoriginate advantageously from a pressure measurement and managementsystem. This type of system is usually provided with pressure andtemperature sensors installed in the wheels or in the tyres of thevehicle. The data are transmitted by radio waves, either continuously,or at regular intervals, or else when a sudden change in the pressureand/or temperature is detected. A receiver and a central processing unitallow the reception and processing of the data. The result of thisprocessing may be used to transmit information to the driver, either inaudible form, and/or in visual form. Accordingly, many tyre pressuremanagement systems are connected to a display which may be dedicated tothis function or a display being used to present various types ofparameters of the vehicle and/or of its environment. The latter case isnormal when the tyre pressure management system is supplied as originalequipment.

Such tyre pressure management systems may also be supplied as anaccessory. They may in this case be fitted to any type of vehicle. Aunit for receiving and processing the radio waves is then installedinside the passenger compartment.

FIG. 1 illustrates the key steps of applying the method and the deviceaccording to the invention. First of all, various data, originating fromthe various sources, are received: the data 20 relating to thetemperature of the tyres, the data 10 relating to the pressure of thetyres of the vehicle and the data 40 relating to the test criteria ifthe latter are not already present in the device.

According to an advantageous embodiment, the latter data may be providedin a permanent manner, and the user does not have to concern himselfwith them. According to a variant embodiment, these data may be suppliedby the user, for example with the aid of a menu provided on the userinterface.

Once the data are available, the device may carry out the test or testsnecessary to detect a possible optimal condition for inflation. Asmentioned above, the device operates advantageously in a loop, in asubstantially continuous manner. In particular, when an optimalcondition for inflation is revealed, it is important to be able to checkif this condition lasts or not. Thanks to this substantially continuousmonitoring, as soon as the optimal condition ceases, the correspondingsignal ceases and the user is informed of this change in the situation.

For the application of the method and of the device according to theinvention, various parameters must be considered. First of all, withrespect to the pressure-related parameters, in addition to the absolutepressure values for each of the tyres, the knowledge of the presence ofa leak, of the pressure levels recommended according to load and/orspeed, and the pressure difference between two tyres positioned on oneand the same axle, may be useful for determining certain situations.

The multiple data items relating to the pressure and the temperature ofthe tyres may be obtained by a tyre pressure measurement and managementsystem.

With or without a tyre pressure measurement and management system, theuseful magnitudes are data associated with or data dependent on thepressure, in this instance called “pressure-related data” or “pressuredata”. These are in particular the following data:

-   -   the real or actual pressure value of at least one of the tyres        of the vehicle;    -   the recommended pressure threshold or thresholds: these are        usually pressure values indicated by the manufacturer of the        vehicle;    -   the presence or absence of a leak: a tyre pressure measurement        and management system or an under-inflation detection module is        capable of taking several measurements of the pressure value        spaced over time. This feature makes it possible to monitor the        change in the pressure value over time. By comparing this change        with preset leakage threshold values, the presence of leaks may        be revealed. For example, a leak of the order of approximately        100 mbar/month may be revealed with great reliability. This type        of leak is often qualified as a “slow” leak since it allows the        vehicle to be used within certain limits. So long as the total        quantity of escaped air does not exceed a certain threshold, the        pressure of the tyre may be within a convenient range of use.        After a certain time, the pressure value is situated below the        recommended pressure value and the module may transmit a warning        signal. At this stage, even if it is a “slow” leak, a corrective        action must be taken very quickly. Larger leaks may evidently        also be detected. A leak of the order of 100 mbar/h or more is        often qualified as a “fast” leak.

1-9. (canceled)
 10. A method for assisting with inflation of tyres for avehicle fitted with a set of tyre pressure sensors, a set of tyretemperature sensors, and a microprocessor, the method comprising:supplying the microprocessor with pressure data relating to a pressureof at least one of the tyres of the vehicle; supplying themicroprocessor with temperature data relating to a temperature of atleast one of the tyres of the vehicle; with aid of the microprocessorsupplied with the pressure data and the temperature data, notifying auser of a possible under-inflation condition present in at least one ofthe tyres of the vehicle; and testing, by the microprocessor, todetermine whether a condition is acceptable for inflation, if averification of an under-inflation condition is received, provided thatsimultaneously: a non-critical under-inflation condition has beendetected for at least one of the tyres of the vehicle, the tyres of thevehicle are not in a hot state, and a state of the tyres of the vehicleis not changed by sun exposure; and, when an acceptable condition forinflation is determined, transmitting a corresponding signal.
 11. Themethod according to claim 10, wherein the non-critical under-inflationcondition corresponds to a measured inflation pressure that is less thana recommended nominal pressure, when cold, by approximately 200 to 400mbar.
 12. The method according to claim 10, wherein test parameters usedin the testing are defined so that the tyres of the vehicle are notconsidered to be in a hot state if a difference between an ambienttemperature and a temperature value of each of the tyres of the vehicledoes not exceed 5° C.
 13. The method according claim 10, wherein testparameters used in the testing are defined so that the tyres of thevehicle are not considered to be in a hot state if there is at least 5°C. of difference between an average of temperatures at a front part ofthe vehicle and an average of temperatures at a rear of part of thevehicle.
 14. The method according to claim 10, wherein test parametersused in the testing are defined so that the tyres of the vehicle are notconsidered to be in a hot state if a difference between a temperature ofa spare wheel tyre and an average temperature of the tyres of thevehicle does not exceed 5° C.
 15. The method according to claim 10,wherein test parameters used in the testing are defined so that a stateof the tyres of the vehicle is not considered to be changed by sunexposure when a maximum temperature difference between a hottest tyreand a coldest tyre does not exceed 5° C.
 16. The method according toclaim 10, wherein test parameters used in the testing are defined sothat a state of the tyres of the vehicle is not considered to be changedby sun exposure when a maximum temperature difference between a hottesttyre and a coldest tyre does not exceed 3° C.
 17. The method accordingto claim 10, wherein, in the testing, the microprocessor receives averification that the tyres of the vehicle are at a temperaturesubstantially close to that measured at a moment when under-inflation isdetected.
 18. The method according to claim 10, wherein, when any of: acondition in which a non-critical under-inflation condition has beendetected for at least one of the tyres of the vehicle, a condition inwhich the tyres of the vehicle are not in a hot state, and a conditionin which a state of the tyres of the vehicle is not changed by sunexposure is no longer satisfied, the signal is no longer transmitted.19. A device for assisting with inflation of tyres of a vehicle, thedevice comprising: an input that receives pressure data of at least oneof the tyres of the vehicle; an input that receives temperature data ofat least one of the tyres of the vehicle; an under-inflation detectionmodule that utilizes the pressure data and the temperature data todetect a possible under-inflation condition present on one or more ofthe tyres of the vehicle; and a testing module that carries out tests todetermine whether a condition is acceptable for inflation, the testsbeing carried with aid of a microcprocessor if a verification of anunder-inflation condition is received, wherein the microprocessor issupplied with the pressure data, the microprocessor is supplied with thetemperature data, the microprocessor determines whether a condition isacceptable inflation if the verification of an under-inflation conditionis received, provided that simultaneously: a non-criticalunder-inflation condition has been detected for at least one of thetyres of the vehicle, the tyres of the vehicle are not in a hot state,and a state of the tyres of the vehicle is not changed by sun exposure,and, when an acceptable condition for inflation is determined, thetesting module transmits a corresponding signal.
 20. The deviceaccording to claim 19, wherein the non-critical under-inflationcondition corresponds to a measured inflation pressure that is less thana recommended nominal pressure, when cold, by approximately 200 to 400mbar.
 21. The device according to claim 19, wherein test parameters usedin the testing module are defined so that the tyres of the vehicle arenot considered to be in a hot state if a difference between an ambienttemperature and a temperature value of each of the tyres of the vehicledoes not exceed 5° C.
 22. The device according claim 19, wherein testparameters used in the testing module are defined so that the tyres ofthe vehicle are not considered to be in a hot state if there is at least5° C. of difference between an average of temperatures at a front partof the vehicle and an average of temperatures at a rear of part of thevehicle.
 23. The device according to claim 19, wherein test parametersused in the testing module are defined so that the tyres of the vehicleare not considered to be in a hot state if a difference between atemperature of a spare wheel tyre and an average temperature of thetyres of the vehicle does not exceed 5° C.
 24. The device according toclaim 19, wherein test parameters used in the testing module are definedso that a state of the tyres of the vehicle is not considered to bechanged by sun exposure when a maximum temperature difference between ahottest tyre and a coldest tyre does not exceed 5° C.
 25. The deviceaccording to claim 19, wherein test parameters used in the testingmodule are defined so that a state of the tyres of the vehicle is notconsidered to be changed by sun exposure when a maximum temperaturedifference between a hottest tyre and a coldest tyre does not exceed 3°C.
 26. The device according to claim 19, wherein, to determine whether acondition is acceptable for inflation, the testing module receives averification that the tyres of the vehicle are at a temperaturesubstantially close to that measured at a moment when under-inflation isdetected.
 27. The device according to claim 19, wherein, when any of: acondition in which a non-critical under-inflation condition has beendetected for at least one of the tyres of the vehicle, a condition inwhich the tyres of the vehicle are not in a hot state, and a conditionin which a state of the tyres of the vehicle is not changed by sunexposure is no longer satisfied, the signal is no longer transmitted.